“Structured light” systems determine the three-dimensional shape of objects. Such systems typically include a projector and a camera separated by a baseline distance. The projector illuminates an object with known light patterns, often series of parallel stripes. The appearance of the patterns as seen by the camera reveals depth information about the object. Structured light is sometimes referred to as “fringe projection” or “pattern projection”. Alternative techniques for shape determination include laser scanning, slit scanning, time-of-flight measurements, and interferometry.
Current structured light systems deliver good performance in terms of depth resolution. However they often require careful lighting control so that pattern detection is not swamped by ambient light. Time-of-flight systems offer better ambient light rejection due to their high modulation frequency, but that frequency also determines the depth resolution. Fine depth resolution with a time-of-flight system may require unrealistically high modulation frequencies.
What is needed is a structured light system offering good depth resolution that also has improved immunity to ambient light in a useful bandwidth.